A veteran cop says he is "appalled" and "devastated" by the vile and sexually aggressive phone call he made to the office of Greens Senator Hanson-Young, in which he spoke about the politician's 11-year-old daughter.

In July, 57-year-old Senior Constable Sean Daniel Murphy consumed a large amount of wine and became angry when he saw Senator Hanson-Young on TV.

Office: "No you cannot. Why do you want a picture of the Senators daughter?"

Murphy: "Because I want to... (10 daily has chosen not to detail the sexual threat, which was said in an aggressive manner).

Office: "You're disgusting (yelling).

On Tuesday in Sydney's Downing Centre Local Court, Murphy pleaded guilty to one charge of using a carriage service to menace, harass or offend.

He didn't appear in person, because he is being treated in a mental health facility.

"He is devastated by what he has done," Murphy's barrister John Davidson said.

"The effect this is had upon his emotional state -- once the reality has come to pass -- has been profound. He is still in hospital, he has been medicated, he is improving, and he thoroughly regrets what he is done."

Murphy joined the NSW Police in 1982, and seven years later was honoured with a Star of Courage for trying to drag a person from a burning building.

But his barrister said three decades on the beat had taken a toll on Murphy's mental health, and he had been under a doctor's care for post traumatic stress disorder.

"In his career he has seen perhaps more bloodshed, more danger, more terrible incidents with children than the public could imagine," Davidson said.

"He has offered to meet the senator and make a personal apology. That has not been accepted. That’s a matter for the senator”

When Federal Police traced the call and questioned Murphy, the officer admitted he'd made a similar call to the senator's Canberra office.

Magistrate Jennifer Atkinson agreed to bar Murphy from contacting either office while he was on bail.

"The distress to the people would have been quite significant," she told the court.

In a statement, Senator Hanson-Young thanked the police.

"In July, in the midst of the public debate regarding comments made by Senator Leyonhjelm about me, a NSW police officer called my office and made a vile threat towards my daughter," she wrote.